A relay node (RN) is considered as a tool to improve, e.g., the coverage of high data rates, group mobility, temporary network deployment, the cell-edge throughput and/or to provide coverage in new areas. The RN is wirelessly connected to a wireless communications network via a donor cell (also referred to as a donor enhanced Node B (donor eNB or D-eNB)).
There may be several kinds of RNs, one kind serves as an eNB to one or more User Equipment (UE). A wireless link between the RN and its served UEs is referred to as an access link and a link between the RN and its donor eNB is named a relay backhaul link.
To a UE that is being served by the RN, the RN appears identical to an eNB, scheduling uplink (UL) and downlink (DL) transmissions from and to the UE over an access link.
The relay backhaul link of an in-band RN typically operates in the same frequency spectrum as the access link. Therefore, due to the RN's transmitter causing interference to its own receiver, simultaneous “donor eNB-to-RN” and “RN-to-UE” or “UE-to-RN” and “RN-to-donor eNB” transmissions on the same time-frequency resource may not be feasible unless sufficient isolation of outgoing and incoming signals is provided, e.g., by means of specific, well separated, and well isolated antenna structures.
In Long Term Evolution (LTE) Advanced proposed by the Third Generation Partnership Project (3GPP), a solution to the interference problem may be handled by operating the RN such that the RN is not transmitting to UEs when it is supposed to receive data from the donor eNB to create gaps in the RN-to-UE transmission. These gaps during which UEs (including Release-8 (Rel-8) UEs) are not supposed to expect any RN transmission are created by configuring Multi-Media Broadcast over a Single Frequency Network (MBSFN) subframes. RN-to-donor eNB transmissions can be facilitated by not allowing any UE-to-RN transmissions in some subframes. Frames and subframes may be considered to be constructs representing time intervals that are used to transmit/receive information.
Furthermore, a UE may require measurement gaps (contiguous periods of time of specified duration) to identify and measure inter-frequency and/or inter-radio access technology (inter-RAT) cells, an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) must provide a single measurement gap pattern with a constant gap duration, i.e., a periodic pattern of measurement gaps, that allows the UE the ability to concurrently monitor all frequency layers and RATs, i.e., available frequency bands. During the measurement gaps, the UE shall not transmit any data, and the UE is not expected to tune its receiver on the E-UTRAN serving carrier frequency.
Hence, there may be a significant number of times when the UE may not receive any data due to the MBSFN subframes and the measurement gaps. Therefore, there may be a desire to reduce the actual number of times when the UE may not receive any data by overlapping the MBSFN subframes and the measurement gaps as much as possible.